The invention relates to a process for the automatic longitudinal guidance of a motor vehicle by way of a longitudinally guiding driver assistance system having a stop-and-go function. Using a detection device of the driver assistance system, information is detected concerning a vehicle driving ahead. By way of the driver assistance system, the motor vehicle is automatically braked to a standing position as a function of the information detected by the detection device. When the new starting-up of the vehicle driving ahead is detected, the motor vehicle is automatically started again possibly as a function of a confirmation signal that can be given by the driver by way of an input device. At least starting from the point in time of the stoppage of the motor vehicle, the vehicle apron is continuously monitored with respect to possible obstacles situated in the vehicle apron by use of a monitoring device having a camera which supplies a sequence of individual images of the vehicle apron.
Such a process is known from EP 2 028 632 A2. In that process, for the detection of obstacles, either differential images are created from a respective first individual image and a second individual image that is taken after the first individual image and are evaluated or, for the detection of obstacles, the vectors of the optical flux of the image information of at least one portion of the image elements of two individual images taken after one another and composed of individual image elements are determined and evaluated.
A similar process is also described in International Patent Document WO 2007/033870 A1.
It is an object of the invention to improve a process for the automatic longitudinal guidance of a motor vehicle with respect to ensuring the safety of the automatic new starting-up.
This and other objects are achieved by a process for the automatic longitudinal guidance of a motor vehicle by a longitudinally guiding driver assistance system having a stop-and-go function, wherein information is detected concerning a vehicle driving ahead by a detection device of the driver assistance system, and wherein, the motor vehicle is automatically braked to a standing position as a function of the information detected by the detection device by the driver assistance system. When a new starting-up of the vehicle driving ahead is detected, the motor vehicle is automatically started again possibly as a function of a confirmation signal that can be given by the driver by way of an input device. Starting at least from the point in time of the stoppage of the motor vehicle, the vehicle apron is continuously monitored with respect to possible obstacles situated in the vehicle apron by a monitoring device comprising a camera which supplies a sequence of individual images of the vehicle apron. For the detection of obstacles in the vehicle apron, characteristic image features are extracted from the individual images and are tracked with respect to time within the sequence of individual images, and (1) an appearance and/or disappearance of one or more characteristic image features taking place in the course of the sequence is determined and evaluated, and/or (2) a change of a spatial distribution of one or more characteristic image features taking place in the course of the sequence in the respective individual image or in a cutout of the respective individual image is determined and evaluated.
For the detection of obstacles in the vehicle apron, according to an aspect of the invention, characteristic image features are extracted from the individual images and are tracked with respect to time within the sequence of individual images, and an appearance and/or disappearance of one or more characteristic image features taking place in the course of the sequence is determined and evaluated. Alternatively or additionally, a change of a spatial distribution of one or more characteristic image features taking place in the course of the sequence in the respective individual image or in a cutout of the latter is determined and evaluated.
The invention is based on the consideration that possible obstacles in the vehicle apron in all probability conceal individual characteristic image features (or the object features on which these characteristic image features are based). The appearance or the disappearance of such a concealment therefore most probably results in the appearance and/or disappearance of one or more, possibly even all characteristic image features. Likewise, the appearance or the disappearance of such a concealment will most probably result in a change of the spatial distribution of individual or all characteristic image features in the respective individual image or in a cutout of the individual image.
When the evaluation of the spatial distribution relates to an image cutout of the respective individual image, this image cutout is preferably defined in a constant manner for the evaluation of the entire sequence. In the simplest case, the image cutout is defined from the outset.
When the evaluation of the spatial distribution relates to an image cutout of the respective individual image, this image cutout is defined according to a preferred embodiment of the present invention by the spatial distribution of the characteristic image features in one or more individual images at the beginning of the sequence.
The evaluation of the spatial distribution preferably takes place such that a so-called feature signature is determined and evaluated from the spatial distribution and possibly additional characteristics of the image features. Preferably, the presence of an obstacle in the vehicle apron is inferred only from significant changes of the spatial distribution or of the feature signature. In the simplest case, the significance of a change can be measured by whether one or more characteristic quantities for the change of the spatial distribution or of the feature signature exceed an absolute or relative threshold.
Suitable characteristic image features are especially the corners and edges in the individual images.
In connection with the evaluation of the appearance and/or disappearance of one or more characteristic image features or in connection with the evaluation of the change of spatial distribution of one or more characteristic image features in the respective individual image or a cutout thereof, an object recognition and/or a scene interpretation is not required and can therefore be eliminated, whereby resources, computing time, energy and the expenditures of the process can be reduced.
The robustness of the process can be increased in that, for the detection of obstacles in the vehicle apron, additionally, differential images are generated and evaluated in each case from a first individual image and a second individual image taken after the first individual image.
The combination of the obstacle recognition on the basis of tracking characteristic image features with such a differential image process is surprising in that the differential image process is essentially based on evaluating image portions or image information of the taken individual images which relate to or show an obstacle, while the obstacle recognition on the basis of tracking characteristic image features is essentially based on evaluating image portions or image information of the taken individual images which specifically relate to or show no obstacles. In other words: as a rule, a differential image process has the purpose of obtaining obstacle information in a direct manner, while obstacles during the tracking of characteristic image features usually represent an interference and are recognized only indirectly because they falsify or hinder the tracking.
The robustness of the process according to the invention can be further increased in that additionally vectors of the optical flux of the image information of at least one portion of the image elements of two individual images taken after one another and composed of individual image elements are determined and evaluated.
Also the combination of the obstacle recognition on the basis of tracking characteristic image features with such a process on the basis of the optical flux is surprising in that the process on the basis of the optical flux is essentially based on evaluating image portions or image information of the taken individual images which relate to or show an obstacle, while the obstacle recognition on the basis of tracking characteristic image features is essentially based on evaluating image portions or image information of the taken individual images which specifically relate to or show no obstacles. In other words: as a rule, a process on the basis of the optical flux is used for obtaining obstacle information in a direct manner, while obstacles during the tracking of characteristic image features usually represent an interference and are recognized only indirectly because they falsify or hinder the tracking.
The robustness of the process according to the invention can be increased to a considerable extent in that, for the detection of obstacles in the vehicle apron, differential images are additionally generated and evaluated in each case from a first individual image and a second individual image taken after the first individual image, and additionally vectors of the optical flux of the image information of at least one portion of the image elements of two individual images taken one after another and composed of individual image elements are determined and evaluated.
When the obstacle recognition on the basis of tracking characteristic image features is combined with such a differential image process and/or such a process on the basis of the optical flux, the individual results of several processes are preferably jointly subjected to a plausibility check in order to determine a total result.
The robustness and/or quality of the process according to the invention can be further increased in that, additionally, signals of further camera devices and/or non-optical sensors at the vehicle, particularly ultrasound-based range sensors, are obtained and evaluated. A fusion of the individual processes can in each case take place on a signal plane, on a result plane or on a plane situated in-between.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing.